Apparatus for operating gaseous discharge devices



March 10, 1959 c. H. BURNS 2,877,332

APPARATUS FOR OPERATING GASEOUS DISCHARGE DEVICES Filed Sept. 25, 1953 WITNESSES: INVENTOR %!7/Q-7 Claude H.Burns.

ATTORNEY APPARATUS FOR OPERATING GASEOUS DISCHARGE DEVICES Claude H. Burns, Lakewood, Ohio, assignor to Westinghouse Electric Corporafion, East Pittsburgh, Pa., a corporation of Pennsylvania Application September 23, 1953, Serial No. 381,853 3 Claims. (Cl. 315-138) This invention relates generally to apparatus for starting and operating gaseous discharge devices, such as fluorescent lamps, and to the manner in which "such apparatus and discharge devices are related, and more specifically to transformer, ballast and heater provisions for such discharge devices having continuously heated cathodes.

When a plurality of electric gaseous discharge devices, of which the fluorescent lamp is one example, are operated together, it has been the practice to energize them from a single low voltage source through a transformer to obtain a higher voltage than the source voltage for starting and operating the lamp. Generally, the transformer is of the autotransformer type, and a plurality of discharge devices may be connected to the transformer secondary, there being a separate ballast in the form of an inductance with a magnetic core connected in series with each lamp to stabilize its operation. Also, in order "to improve the power factor and to correct for str'obo- 'scopic effect, the circuit of one discharge device is made'a leading circuit by the inclusion of a series capacitor. 'Heretofore, discharge devices having continuously heated electrodes have in some instances resorted to separate windings inductively connected to the autotr-ans'form'er'in order'to obtain energy for heating the lamp cathodes. -Such separate windings require additional material, labor, and manufacturing time, and in some instances have resulted in considerably larger and heavier assemblies. Also, by using externally coupled windings for energizing the cathodes of a gaseous discharge device, for the amount of copper used it is not possible to obtain the greatest open circuit voltage across the discharge devices.

Accordingly, one object of my invention is to provide -a novel unitary combined transformer and ballast assembly for the control of a plurality of gaseous dischargedevices' of the continuously heated cathode type, which is less in weight and size than has heretofore been employed.

Another object of my invention is to provide a novel u'nitary combined transformer and ballast assembly for the control of a plurality of gaseous discharge devices of the'continuously heated cathode type wherein each winding for energizing such cathodes is an extension of the windings of the 'autotransformer.

Another object of my invention is to provide a novel Unitary combined transformer and ballast assembly forthe control of a plurality of gaseous discharge devices "of the continuously heated cathode type wherein one cathode of each discharge device is energized by an extension of separate windings of an autotransformer-and. the other cathode of each discharge device is energized. by another extension of a separate winding of the auto-- transformer.

A further object of my invention is .to provide anovel assembly of the transformer, ballast and heater windings on ;a single ,core for controlling the operation of a plu-- --f; gase0,l1S discharge devices having continuously heated cathodes.

* tates Patent 0 2,877,382 Patented Mar. 10, 1959 Still another object of my invention is to provide a novel unitary combined transformer and ballast assembly for the control of a plurality of gaseous discharge devices or the continuously heated cathode type, wherein the ghest open circuit voltage for a given amount of -opper used is obtained across each discharge device.

These and other objects of my invention will become more apparent upon consideration of the following detailed description of a preferred embodiment of my invention whentaken in connection with the drawing in which is illustrated a schematic view of a transformer, ballast, and heater winding assembly for the control of gaseous electric discharge devices constructed in accordance with the principles of my invention, together with a circuit for connecting it to the discharge devices.

In accordance with my invention, the transformer, 'ba'llast, and cathode sheater windings for controlling the operation of a plurality of gaseous discharge devices, such as fluorescent lamps, are all assembled on a common core structure. While this invention is hereinafter specifically described in connection with the operation of a .pair of lamps, it is not limited to this specific number of lamps butmay be embodied in the control for operation of a single lamp, or for a :greaternumber of lamps. The windings for operation of a pair of lamps are assembled in a manner such that the ballast coil for the lag lamp is in the same magnetic circuit with the autotransformer, whereas the ballast coil for the lead lamp :is outside the magnetic circuit for the autotransformer windings, but employs as part of its magnetic circuit a portion of the magnetic circuit for the autotransformer. The various windings u'tilized in heating the cathodes of the discharge deviceare-all extensions of certain of these windings. :From the following detailed description, the benefits obtainable from such .a design with respect to the open circuit voltageacross the-discharge devices and with respect to reduction in component parts .and materials will become apparent- The transformer and .ballast assembly shown in the drawing is supported on an elongated core structure 4 which :may be fabricated from a plurality of stacked laminations, and includes :a central, longitudinally extending winding 'leg'porti'on 6, and a pair of yoke portions 8 positioned at opposite sides of the winding leg portion 6. Although thecore "structure '4 is herein described as composed of three parts, forming the winding leg portion '6 :and :yoke portions '8, :respectively, this specific arrangement, per se, forms no 'part of my invention but 'is more specifically described and claimed .in the pending application Serial .No. 267,628 of Oglesbee and Cornelhfiled Januaryv22, 1952, on Cores, and'which is assigned to the .same assignee as this application. For the broad purposes of my-invention, each lamination'may be constructed in oneintegral piece, though preferablyit is of more than one .piece, "such as the three herein illustrated.

The core structured has three pairs of opposed :openings 12, 14 and '1'6-providedin'the yoke portion 8 thereof at opposite sides of the winding leg portion 6, .and spaced along-the length .of the core structure, with the opposed openings 12 adapted to receive a lag coil .18 woundon winding leg portion '6. Theopposed openings '14 are-for the purpose of receiving the autotransformer winding 20 which .is wound on the winding leg portion 6, and the oppiosedopenings :16 {are for the purpose of-re- 'ceiving 'a lead =;coil 22 2150 wound-on winding leg portion 6 at the location -of openings 16. Intermediatelag .coil :18 and the autotransformerwinding 20, the yoke portions of the-:core structure are provided with opposed legs24 which extendinwardlyttoward winding leg portion 6 but terminates short-tll ereofito form a leakagegap .in

the-core stucturetbetween theopeniugs :12 and 14. The

3 yoke portions 8 of the core structure also have inwardly extending opposed leg portions 26 which extend into en gagement with the winding leg portion 6 at the left end of the core structure, and inwardly'extending leg portions 28 likewise extending into engagement with winding leg portion 6. Leg portions 28 are located between the autotransformer winding 20 and the lead coil 22 adacent the right-hand end of the core structure, as viewed in the drawing. Yoke portions 8 have opposed inwardly extending legs 30 which may, if desired, ter- .minate short of each other and are spaced from the righthand end of winding leg 6 whereby a gap 31 will be formed between the right-hand end of the winding leg portion 6 and the legs 30 of the yoke portion 3.

When the core structure 4 is formed of three-piece laminations, as illustrated in the drawing and as is more particularly pointed out in the above-mentioned pending 7 application, the laminations may be secured together in' any desired manner, preferably as by welding them at three exterior junctions of the three parts of each lamina tion, namely, at the junctions 48 and 50 between the legs 26 of the yoke portion 8 and the adjacent end of winding 6 leg portion 6, and gap 52 between the legs 30 of yoke portion 8. If desired, additional securing means, such as bolts, not shown, which may extend through aligned apertures in winding leg portion 6, may also be employed. As shown, the various windings of the transformer and ballast assembly are electrically connected to a pair' of fluorescent lamps 60 and 62, each of which has at each of its ends outwardly extending terminals 32 which are adapted to engage contacts 34mounted in lamp holders 36. Each lamp has a cathode located at each of its ends, whch is connected between the lamp terminals 32. Although all the cathodes of each lamp 60 and 62 may be identical,'for the sake of clarity in describing the illustrative embodiment of my invention, separate identifying numerals have been assigned to each cathode. Thus, as shown in the drawing, the cathodes at the top of lamps 60 and 62 have been designated as cathodes 38 and 40, and those at the bottom as 42-and 44, respectively. Such fluorescent lamps are generally installed where they are to'be operated from a low voltage supply source, such as 118 or 236 volts commonly supplied customers of electricity, and such a source of supply may be connected to supply conductors 54 and 56, either of which may be controlled by a switch, not shown, inserted in series circuit relation therewith.

In order to start such lamps rapidly, it is necessary that the cathodes at each end of each lamp be initially heated in order to partially ionize the gas within the lamp to assist in initiating a discharge across the lamp. Once such a discharge occurs, it is no longer necessary that the lamp cathodes be heated from an external source as the arc current of the lamp will thereafter maintain the cathode heated. In view of the minor losses incurred, and the relatively high cost of providing means for disconnecting the cathode heating circuits, it has been found to be practical to heat the cathodes continuously, even though such external heating is not required during the period that a discharge occurs across the lamp.

It will be observed from the drawing that the transformer winding 20 is in the form of an autotransformer having a winding 46 connected between the supply conductors 54 and 56. Supply conductor 56 is also connected by means of a conductor 68, having a condenser 70 therein to the lead coil 22 which, in turn, by means winding 58 to the supply conductor 54. As lag C011 18 of conductor 72 is connected to the winding 64 of the autotransformer. Winding 64 is connected by means of conductor 74 and a lamp holder-36 to one of'the terminals 32 of lamp which is connected to cathode 40.

The other terminal 32 of lamp 60 which is connected to the cathode 40 is connected through lamp holder 36 by a conductor 76 to an extension 66 of winding 64. Supply conductor 56 is also connected by a conductor 78 to the lag coil 18 which in turn is connected to a terminal 32 legs 24 of the yoke portions of lamp 62 which is connected to cathode 38 by a con ductor 80 and a lamp holder 36. The other terminals 32 of lamp 62 connected to the cathode 38 is connected by conductor 82 to an extension of the lag coil 18. In order to energize cathodes 42 and 44 of lamps 62 and 60 respectively, supply conductor 54 is connected to a conductor 88 which in turn is connected through lamp holders 36 to one of the terminals 32 of each lamp. Winding 46 is provided with an extension 58 from supply conductor 54 which is connected by a conductor 84 to the other terminals 32 of each lamp connected to the cathodes 42 and 44. Although the particular circuit for heating cathodes 42 and 44 as described is a parallel arrangement, if desired a series circuit may be utilized.

It will be noted that the transformer winding 20 com prising windings 46 and 64 and extension windings 58 and 66 is in autotransformer relationship with winding 46 serving as a primary winding portion. Thus when supply conductors 54 and 56 are energized, extension winding 58 functions as a portion of an autotransformer secondary and a resultant cathode heating current flows through conductor 84, cathodes 42 and 44 in parallel and conductor 88 to the supply conductor 54. In a similar manner extension winding 66 induces a current flow through conductor 76, cathode 40 and conductor 74. It will also be noted that lag coil 18 as more particularly described hereinafter is in the same mag netic circuit as winding 46 and that such windings also function as an auto-transformer. Thus extension winding 90 of lag coil 18 functions in a similar manner to induce a current flow through conductor 82, cathode 38 and conductor 80. By such a construction there is a current flow through each cathode of each lamp which enables each cathode to become heated when winding 46 is energized. Such current flow through the cathodes causes the gas within the lamps to become partially ionized, whereby a lower voltage can be utilized to start and maintain a discharge across the lamp cathodes.

As has been indicated, core 4 provides a low reluctance magnetic circuit comprising the parts of winding leg por tion 6 and yoke portions 8 between'the legs 26 and 28 as well as these legs themselves. Windings 64 and 66 together with the winding 46 are connected across the lamp 60 in autotransformer relationship so that the voltage in windings 66 and 64 is added to that of winding 46 to thus provide the necessary high voltage for operation of the lamp 60, once the adjacent end of winding leg portion 6 of the core 4 determines the reactance for coil 22. The gap between legs 30 themselves, while not essential, is desirable; to

, insure proper assembly of the parts of each lamination,

particularly to insure proper engagement of yoke legs 26 and 28 with winding leg 6, and thus properly determine the gaps between yoke legs 24 and winding leg 6.

The operating circuit for lamp 62 comprises supply conductor 54, winding 46, conductor 78, lag coil 18,

extension 90, conductor 82, lamp 62, conductor 84 and is in the same magnetic circuit as winding 46, the voltage of the two is additive which provides the necessary high .voltage needed for operation of the lamp, 62 once lamp 62 has been suificiently ionized by the heated cathodes 38 and 42 to permit a discharge at that voltage. Lag

coil 18, however, acts somewhat differently than the winding 64 of the transformer winding 20, in that'the of the core provide for magnetic leakage between windings 46 and the lag coil 18, and the gap between these legs and the winding leg portion 6 provides for a high reactance for the lag circuit containing lag coil 18. Lag coil 18 may be designed to produce in conjunction with winding 46 a starting and operating voltage for the lamp 62 which will be substantially the same as that provided by the autotransformer for lamp 60. The lag coil 18 also provides a reactance in series with lamp 62 of a value comparable to that provided for lamp 60 by lead coil 22 and capacitor 70. As lag coil 18 provides a relatively high reactance in the circuit for lamp 62, it will be apparent that the current in this lamp will lag behind that of the source of supply, whereas the condenser 70 in the circuit for lamp 60 will cause the current in this circuit to lead that of the source of supply to thus supply a relatively high power factor and correction for the stroboscopic eifect of the lamps.

In operation, the voltage available for starting lead lamp 62 will be somewhat in excess of that provided for operating lamp 60 due to the common portion of the magnetic circuit comprising legs 28 of yoke portions 8 which may be restricted in cross-sectional area so that they partly saturate during the open circuit condition of the lead lamp 60. By properly phasing the lead coil 22 with respect to winding 46, that is, by winding so that the induced flux is additive, the open circuit voltage applied to lamp 60 will be substantially higher than the output voltage of the autotransfonner due to some of the flux generated by winding 46 linking with the lead coil 22. By employing this expedient the size of the windings may be reduced for any given circuit voltage requirement of lamp 60, while the required voltage for lamp 62 may still be achieved by appropriately designing lag coil 18. Once lamp 60 starts the flux in reduced area legs 28 decreases, it then being the vector difierence between the autotransformer flux and that of lead coil 22. Once lamp 60 starts the coupling between the autotransformer and the lead coil 22 will be reduced, so that for all practical purposes the lead coil 22 operates as an entirely separate unit from the autotransformer.

The transformer and ballast assembly described above has been found to be more economical in construction than has heretofore been practical and has resulted in very substantial savings in the amount of copper and iron employed, thus reducing losses as well as the size and weight of the assembly. It will be noted particularly that each cathode is heated by an extension winding which results in considerable savings in fabricating costs as only a tap need be provided on a single winding rather than providing a separate heater winding. Also by utilizing such extensions instead of separate heating coils, the open circuit voltage across the lamps will be increased by the amount of voltage generated across such extensions. Thus for a given amount of copper used in the coils a greater open circuit voltage can be obtained than is obtained with non-extension types of heater windings.

From this description of my invention it will be noted that I have provided a transformer ballast assembly for a discharge device having continuously heated cathodes wherein all of the heater windings for each of the cathodes of each lamp is an extension of an autotransformer winding. It will be noted that only one unitary structure is provided and that no auxiliary apparatus is required external of the transformer and ballast assembly. It is believed apparent that by st: providing a unitary structure a substantial savings in fabricating and installing such devices can be achieved. Accordingly having described a preferred embodiment of the invention in accordance with the patent statutes, it is desired that the invention be not limited to the specific construction illustrated, inasmuch as it will be apparent that many modifications may be made without departing from the spirit and scope of my invention. Accordingly it is desired that this invention be interpreted as broadly as possible and that it be limited only as required by the prior art.

I claim as my invention:

1. Apparatus for controlling the operation of at least one pair of gaseous discharge devices comprising an autotransformer having a core, a primary winding and a closely coupled low reactance secondary winding both of which are mounted on said core and connected in autotransformer relation, a pair of spaced lampholders each having two contacts, a loosely coupled high reactance ballast winding electrically connected in series in the connection between said primary and secondary windings, a first winding extending from the free end of said secondary winding and connected across the contacts of one of said lampholders for impressing a low voltage thereon, and a second winding extending from the free end of said primary winding and connected across the contacts of the other of said lampholders for impressing a low voltage thereon, while at the same time impressing a high voltage across said lampholders.

2. The apparatus of claim 1 having a second pair of spaced lampholders each having two contacts, a high reactance secondary winding also mounted on said core with one end connected to the same side of said primary winding as said low reactance secondary, means connecting an outer end portion of said high reactance secondary Winding to the contacts of one lampholder of said second pair of lampholders, and means connecting said second winding to the contacts of the other lampholder of said second pair of lampholders.

3. The apparatus of claim 1 having a second pair of spaced lampholders each having two contacts, a high reactance secondary winding also mounted on said core with one end connected to the same side of said primary winding as said l-ow reactance secondary, means conmeeting the other end of said high reactance secondary winding to a contact of one lampholder of said second pair of lampholders, and means connecting said second winding to the contacts of the other lampholder of said second pair of lampholders.

References Cited in the file of this patent UNITED STATES PATENTS 2,025,471 Osborne Dec. 24, 1935 2,269,978 Kronmiller Jan. 13, 1942 2,496,981 Boucher Feb. 7, 1950 2,504,548 Lemmers Apr. 18, 1950 2,504,549 Lemmers Apr. 18, 1950 2,552,111 Peterson May 8, 1951 2,644,107 Keitfer June 30, 1953 

